Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async process like this:

 sub some_func : Coro {
    # some more async code
 }

 cede;

=head1 DESCRIPTION

This module collection manages coroutines. Coroutines are similar to
Threads but don't run in parallel.

This module is still experimental, see the BUGS section below.

In this module, coroutines are defined as "callchain + lexical variables
+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
callchain, it's own set of lexicals and it's own set of perl's most
important global variables.

=cut

package Coro;

use Coro::State;

use base Exporter;

$VERSION = 0.12;

@EXPORT = qw(async cede schedule terminate current);
@EXPORT_OK = qw($current);

{
   my @async;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      Coro->export_to_level(1, @_);
      my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
      *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
         my ($package, $ref) = (shift, shift);
         my @attrs;
         for (@_) {
            if ($_ eq "Coro") {
               push @async, $ref;
            } else {
               push @attrs, $_;
            }
         }
         return $old ? $old->($package, $ref, @attrs) : @attrs;
      };
   }

   sub INIT {
      &async(pop @async) while @async;
   }
}

=item $main

This coroutine represents the main program.

=cut

our $main = new Coro;

=item $current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).

=cut

# maybe some other module used Coro::Specific before...
if ($current) {
   $main->{specific} = $current->{specific};
}

our $current = $main;

sub current() { $current }

=item $idle

The coroutine to switch to when no other coroutine is running. The default
implementation prints "FATAL: deadlock detected" and exits.

=cut

# should be done using priorities :(
our $idle = new Coro sub {
   print STDERR "FATAL: deadlock detected\n";
   exit(51);
};

# this coroutine is necessary because a coroutine
# cannot destroy itself.
my @destroy;
my $manager = new Coro sub {
   while() {
      delete ((pop @destroy)->{_coro_state}) while @destroy;
      &schedule;
   }
};

# we really need priorities...
my @ready; # the ready queue. hehe, rather broken ;)

# static methods. not really.

=head2 STATIC METHODS

Static methods are actually functions that operate on the current process only.

=over 4

=item async { ... } [@args...]

Create a new asynchronous process and return it's process object
(usually unused). When the sub returns the new process is automatically
terminated.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

The coderef you submit MUST NOT be a closure that refers to variables
in an outer scope. This does NOT work. Pass arguments into it instead.

=cut

sub async(&@) {
   my $pid = new Coro @_;
   $manager->ready; # this ensures that the stack is cloned from the manager
   $pid->ready;
   $pid;
}

=item schedule

Calls the scheduler. Please note that the current process will not be put
into the ready queue, so calling this function usually means you will
never be called again.

=cut

my $prev;

sub schedule {
   # should be done using priorities :(
   ($prev, $current) = ($current, shift @ready || $idle);
   Coro::State::transfer($prev, $current);
}

=item cede

"Cede" to other processes. This function puts the current process into the
ready queue and calls C<schedule>, which has the effect of giving up the
current "timeslice" to other coroutines of the same or higher priority.

=cut

sub cede {
   $current->ready;
   &schedule;
}

=item terminate

Terminates the current process.

Future versions of this function will allow result arguments.

=cut

sub terminate {
   push @destroy, $current;
   $manager->ready;
   &schedule;
   # NORETURN
}

=back

# dynamic methods

=head2 PROCESS METHODS

These are the methods you can call on process objects.

=over 4

=item new Coro \&sub [, @args...]

Create a new process and return it. When the sub returns the process
automatically terminates. To start the process you must first put it into
the ready queue by calling the ready method.

The coderef you submit MUST NOT be a closure that refers to variables
in an outer scope. This does NOT work. Pass arguments into it instead.

=cut

sub _newcoro {
   terminate &{+shift};
}

sub new {
   my $class = shift;
   bless {
      _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
   }, $class;
}

=item $process->ready

Put the current process into the ready queue.

=cut

sub ready {
   push @ready, $_[0];
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - could be faster, especially when the core would introduce special
   support for coroutines (like it does for threads).
 - there is still a memleak on coroutine termination that I could not
   identify. Could be as small as a single SV.
 - this module is not well-tested.
 - if variables or arguments "disappear" (become undef) or become
   corrupted please contact the author so he cen iron out the
   remaining bugs.
 - this module is not thread-safe. You must only ever use this module from
   the same thread (this requirement might be loosened in the future to
   allow per-thread schedulers, but Coro::State does not yet allow this).

=head1 SEE ALSO

L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
L<Coro::L<Coro::Handle>, L<Coro::Socket>.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.25
Committed:	Wed Jul 25 21:12:57 2001 UTC (22 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.24:	+2 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.8	Coro - coroutine process abstraction
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Coro;
8
9	root	1.8	async {
10			# some asynchronous thread of execution
11	root	1.2	};
12
13	root	1.8	# alternatively create an async process like this:
14	root	1.6
15	root	1.8	sub some_func : Coro {
16			# some more async code
17			}
18
19	root	1.22	cede;
20	root	1.2
21	root	1.1	=head1 DESCRIPTION
22
23	root	1.14	This module collection manages coroutines. Coroutines are similar to
24			Threads but don't run in parallel.
25
26			This module is still experimental, see the BUGS section below.
27
28	root	1.20	In this module, coroutines are defined as "callchain + lexical variables
29	root	1.23	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
30			callchain, it's own set of lexicals and it's own set of perl's most
31			important global variables.
32	root	1.22
33	root	1.8	=cut
34
35			package Coro;
36
37			use Coro::State;
38
39			use base Exporter;
40
41	root	1.24	$VERSION = 0.12;
42	root	1.8
43	root	1.22	@EXPORT = qw(async cede schedule terminate current);
44	root	1.8	@EXPORT_OK = qw($current);
45
46			{
47			my @async;
48
49			# this way of handling attributes simply is NOT scalable ;()
50			sub import {
51			Coro->export_to_level(1, @_);
52			my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
53			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
54			my ($package, $ref) = (shift, shift);
55			my @attrs;
56			for (@_) {
57			if ($_ eq "Coro") {
58			push @async, $ref;
59			} else {
60	root	1.17	push @attrs, $_;
61	root	1.8	}
62			}
63	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
64	root	1.8	};
65			}
66
67			sub INIT {
68	root	1.20	&async(pop @async) while @async;
69	root	1.8	}
70			}
71
72			=item $main
73	root	1.2
74	root	1.8	This coroutine represents the main program.
75	root	1.1
76			=cut
77
78	root	1.9	our $main = new Coro;
79	root	1.8
80	root	1.19	=item $current (or as function: current)
81	root	1.1
82	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
83	root	1.1
84	root	1.8	=cut
85
86			# maybe some other module used Coro::Specific before...
87			if ($current) {
88			$main->{specific} = $current->{specific};
89	root	1.1	}
90
91	root	1.9	our $current = $main;
92	root	1.19
93			sub current() { $current }
94	root	1.9
95			=item $idle
96
97			The coroutine to switch to when no other coroutine is running. The default
98			implementation prints "FATAL: deadlock detected" and exits.
99
100			=cut
101
102			# should be done using priorities :(
103			our $idle = new Coro sub {
104			print STDERR "FATAL: deadlock detected\n";
105			exit(51);
106			};
107	root	1.8
108	root	1.24	# this coroutine is necessary because a coroutine
109			# cannot destroy itself.
110			my @destroy;
111			my $manager = new Coro sub {
112			while() {
113			delete ((pop @destroy)->{_coro_state}) while @destroy;
114			&schedule;
115			}
116			};
117
118	root	1.8	# we really need priorities...
119	root	1.16	my @ready; # the ready queue. hehe, rather broken ;)
120	root	1.8
121			# static methods. not really.
122
123			=head2 STATIC METHODS
124
125			Static methods are actually functions that operate on the current process only.
126
127			=over 4
128
129	root	1.13	=item async { ... } [@args...]
130	root	1.8
131			Create a new asynchronous process and return it's process object
132			(usually unused). When the sub returns the new process is automatically
133			terminated.
134
135	root	1.13	# create a new coroutine that just prints its arguments
136			async {
137			print "@_\n";
138			} 1,2,3,4;
139
140			The coderef you submit MUST NOT be a closure that refers to variables
141			in an outer scope. This does NOT work. Pass arguments into it instead.
142
143	root	1.8	=cut
144
145	root	1.13	sub async(&@) {
146			my $pid = new Coro @_;
147	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
148	root	1.11	$pid->ready;
149			$pid;
150	root	1.8	}
151	root	1.1
152	root	1.8	=item schedule
153	root	1.6
154	root	1.8	Calls the scheduler. Please note that the current process will not be put
155			into the ready queue, so calling this function usually means you will
156			never be called again.
157	root	1.1
158			=cut
159
160	root	1.8	my $prev;
161
162			sub schedule {
163	root	1.9	# should be done using priorities :(
164			($prev, $current) = ($current, shift @ready \|\| $idle);
165	root	1.8	Coro::State::transfer($prev, $current);
166	root	1.1	}
167
168	root	1.22	=item cede
169	root	1.1
170	root	1.22	"Cede" to other processes. This function puts the current process into the
171			ready queue and calls C<schedule>, which has the effect of giving up the
172			current "timeslice" to other coroutines of the same or higher priority.
173	root	1.7
174	root	1.8	=cut
175
176	root	1.22	sub cede {
177	root	1.8	$current->ready;
178			&schedule;
179			}
180	root	1.7
181	root	1.8	=item terminate
182	root	1.7
183	root	1.8	Terminates the current process.
184	root	1.1
185	root	1.13	Future versions of this function will allow result arguments.
186
187	root	1.1	=cut
188
189	root	1.8	sub terminate {
190	root	1.23	push @destroy, $current;
191	root	1.24	$manager->ready;
192	root	1.23	&schedule;
193			# NORETURN
194	root	1.1	}
195	root	1.6
196	root	1.8	=back
197
198			# dynamic methods
199
200			=head2 PROCESS METHODS
201
202			These are the methods you can call on process objects.
203	root	1.6
204	root	1.8	=over 4
205
206	root	1.13	=item new Coro \&sub [, @args...]
207	root	1.8
208			Create a new process and return it. When the sub returns the process
209			automatically terminates. To start the process you must first put it into
210			the ready queue by calling the ready method.
211	root	1.6
212	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
213			in an outer scope. This does NOT work. Pass arguments into it instead.
214
215	root	1.6	=cut
216
217	root	1.13	sub _newcoro {
218			terminate &{+shift};
219			}
220
221	root	1.8	sub new {
222			my $class = shift;
223			bless {
224	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
225	root	1.8	}, $class;
226			}
227	root	1.6
228	root	1.8	=item $process->ready
229	root	1.1
230	root	1.8	Put the current process into the ready queue.
231	root	1.1
232	root	1.8	=cut
233	root	1.1
234	root	1.8	sub ready {
235			push @ready, $_[0];
236			}
237	root	1.1
238	root	1.8	=back
239	root	1.2
240	root	1.8	=cut
241	root	1.2
242	root	1.8	1;
243	root	1.14
244	root	1.17	=head1 BUGS/LIMITATIONS
245	root	1.14
246			- could be faster, especially when the core would introduce special
247			support for coroutines (like it does for threads).
248			- there is still a memleak on coroutine termination that I could not
249			identify. Could be as small as a single SV.
250			- this module is not well-tested.
251	root	1.17	- if variables or arguments "disappear" (become undef) or become
252			corrupted please contact the author so he cen iron out the
253			remaining bugs.
254			- this module is not thread-safe. You must only ever use this module from
255			the same thread (this requirement might be loosened in the future to
256	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
257	root	1.9
258			=head1 SEE ALSO
259
260			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
261	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
262			L<Coro::L<Coro::Handle>, L<Coro::Socket>.
263	root	1.1
264			=head1 AUTHOR
265
266			Marc Lehmann <pcg@goof.com>
267			http://www.goof.com/pcg/marc/
268
269			=cut
270